1. Field of the Invention
The present invention relates to the field of liquid metering rolls, and more particularly rolls for metering inks, adhesives or like fluids.
2. Description of the Prior Art
In the printing art, it is known to provide an ink metering roll for the transfer of ink from a reservoir to the print roller. The ink roller comprises a cylindrical core having formed on its cylindrical outer surface, a plurality of spaced apart ink capturing cells. The quantity of ink deposited on the print roller is controlled by the tolerances associated with the cells, namely, their size, configuration and spacing. See U.S. Pat. No. 3,613,578. It will be appreciated that the construction of an ink metering roll with precisely shaped ink capturing cells formed in high concentrations is a costly apparatus from the standpoints of the procedures utilized to manufacture same. The cost justified from the standpoint of the quality of printing which is achieved.
However, ink metering rolls are subject to corrosive attack as a result of the inks which are employed in the printing process and their particular pH, and are subject to rapid wear because of their continued use.
U.S. Pat. No. 4,009,658 to Heurich attempted to improve the life of the ink metering roll through the use of a plasma flame deposit procedure. Heurich taught to form the cylindrical core and engrave the plurality of ink capturing cells onto the core and thereafter subject the core to a flame deposit procedure in which a ceramic coating would be applied to the exposed surfaces of the core including the cell surfaces. While this has improved the life expectancy of the ink metering roller, it is an expensive, time-consuming process which does have certain drawbacks.
Once you have obtained a concentric roller that has been appropriately engraved with the ink capturing cells, a bonding coat utilizing 95-5 nickel must be applied to help anchor the subsequent ceramic, such as chrome oxide. The chrome oxide is sprayed on the roller utilizing the plasma flame deposit procedure, this procedure taking from 6 to 8 hours. Further, the procedure contributes to a waste of chrome oxide in the spraying procedure.
The coating, after application, does have some porosity so the corrosive attack on the underlying roller from the inks is not completely eliminated. Still further, it is oftentimes difficult to get a consistent coating about the entire periphery of the roll. Further, if contaminants are present in the spray, such as copper or a free chromium ion, it will be rejected by the roll and will result in uneven coating.
Even after the coating has been applied, and even if it has been applied consistently about the periphery of the roll, it still is subject to cracks and penetration if it comes into contact with a foreign object, stress cracking during operation if the roll overhears and delamination if any of the foregoing occur.
Applicant's invention eliminates the need for the application of a coating, and provides superior protection to possible corrosion of the underlying metal core due to the superior anti-porous nature of the roll and ensures a uniform cylinder onto which the ink capturing cells can be engraved in a lineal, cells per inch format greater than can be presently achieved. While applicant has described the prior art as it related to liquid metering rolls for ink, metering rolls are also utilized to meter other liquids including adhesives and applicant's invention would have similar application.